WO2007086657A1 - Backlight unit and lcd having the same - Google Patents

Backlight unit and lcd having the same Download PDF

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Publication number
WO2007086657A1
WO2007086657A1 PCT/KR2007/000033 KR2007000033W WO2007086657A1 WO 2007086657 A1 WO2007086657 A1 WO 2007086657A1 KR 2007000033 W KR2007000033 W KR 2007000033W WO 2007086657 A1 WO2007086657 A1 WO 2007086657A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
guide plate
light emitting
liquid crystal
backlight unit
Prior art date
Application number
PCT/KR2007/000033
Other languages
French (fr)
Inventor
Myong Rock Oh
Original Assignee
Lg Innotek Co., Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from KR1020060007186A external-priority patent/KR20070077574A/en
Priority claimed from KR1020060007185A external-priority patent/KR20070077573A/en
Application filed by Lg Innotek Co., Ltd filed Critical Lg Innotek Co., Ltd
Publication of WO2007086657A1 publication Critical patent/WO2007086657A1/en

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/005—Means for improving the coupling-out of light from the light guide provided by one optical element, or plurality thereof, placed on the light output side of the light guide
    • G02B6/0053—Prismatic sheet or layer; Brightness enhancement element, sheet or layer
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
    • G02B6/0011—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems the light guides being planar or of plate-like form
    • G02B6/0033—Means for improving the coupling-out of light from the light guide
    • G02B6/0056—Means for improving the coupling-out of light from the light guide for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements

Definitions

  • the present invention relates to a backlight unit and a liquid crystal display (LCD) device having the same.
  • Background Art
  • a cathode ray tube (CRT) display device has been most widely used until recently as one of display devices for displaying image data on a screen.
  • the CRT display device causes a lot of inconvenience due to its large volume and heavy weight for its display area.
  • a thin film type flat panel display device which has a slim profile and a large display area and thus can be used conveniently anywhere, has been developed and is gradually replacing the CRT.
  • a liquid crystal display (LCD) device is one of the thin film type flat panel display devices, which are widely used at the present time.
  • the LCD device uses optical anisotropy and polarization properties of liquid crystal molecules. Alignment of liquid crystal molecules has a specific direction and polarization properties because a liquid crystal has a thin and long structure.
  • the alignment direction can be controlled by applying an electric field to the liquid crystal. Accordingly, when the alignment direction is controlled, due to the optical anisotropy of the liquid crystal, light rays may pass through or be cut off by the liquid crystal according to the alignment direction of the liquid crystal molecules so that colors and images are displayed.
  • the liquid crystal display device generally uses light provided by an external light source or a backlight unit to display images because the liquid crystal is not self-luminous.
  • An embodiment of the present invention provides a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile.
  • An embodiment of the present invention provides an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile.
  • An embodiment of the present invention provides a backlight unit comprising: a light guide plate; a light emitting element for providing the colored light to the light guide plate; a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light; and a transflective polarizing prism sheet formed on the fluorescent exciting sheet.
  • An embodiment of the present invention provides a liquid crystal display device comprising: a backlight unit having a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; and a second polarizer formed on the liquid crystal panel.
  • An embodiment of the present invention provides a mobile communication terminal comprising: a backlight unit having a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; a second polarizer formed on the liquid crystal panel; a communication unit for performing communication with an outside; and a control unit for controlling the backlight unit, the liquid crystal panel, and the communication unit.
  • the present invention it is possible to provide a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile.
  • a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile.
  • an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile.
  • FIG. 1 is a schematic view illustrating a backlight unit according to an embodiment of the present invention
  • FIG. 2 is a schematic view illustrating a liquid crystal display device according to an embodiment of the present invention.
  • FIG. 1 is a schematic view illustrating a backlight unit according to an embodiment of the present invention.
  • a backlight unit includes a light emitting element 11, a light guide plate 13, a fluorescent exciting sheet 15, and a transflective polarizing prism sheet 17.
  • the light emitting element 11 may provide the light guide plate with blue light.
  • the light emitting element 11 may be realized as, for example, a blue light emitting diode. Blue light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15.
  • a pattern may be formed on a lower surface of the light guide plate 13.
  • projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15.
  • a reflector may be further formed on a lower portion of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
  • the fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light.
  • the fluorescent exciting sheet 15 may be realized to include a yellow phosphor or a red/green phosphor.
  • the phosphor may be contained inside the fluorescent exciting sheet 15 or coated on outer surfaces of the fluorescent exciting sheet 15.
  • the light emitting element 11 may provide blue/green light.
  • the light emitting element 11 may be realized as a blue light emitting diode and a green light emitting diode. Also, the light emitting element 11 may be realized to be mounted as a light emitting diode package including a blue light emitting chip and a green light emitting chip. The blue/green light may be expressed as cyan light.
  • Blue/green light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15.
  • a pattern may be formed on a lower surface of the light guide plate 13.
  • projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15.
  • a reflector may be further formed on a lower surface of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
  • the fluorescent exciting sheet 15 receives blue/green light emitted from the light emitting element 11 to emit white light.
  • the fluorescent exciting sheet 15 may be realized to include a red phosphor.
  • the phosphor may be contained inside the fluorescent exciting sheet 15 or coated on outer surfaces of the fluorescent exciting sheet 15.
  • a backlight unit has 30 % higher brightness when using the transflective polarizing prism sheet 17 than when using a general prism sheet.
  • Upper surface of the transflective polarizing prism sheet 17 has a prism shape.
  • White light emitted from the fluorescent exciting sheet 15 is unpolarized light including both a polarization component in a first direction (Pl) and a polarization component in a second direction (P2).
  • the transflective polarizing prism sheet 17 transmits light having the polarization component in the first direction (Pl), whereas reflects light having the polarization component in the second direction (P2) according to a characteristic of the polarization axis thereof.
  • a backlight unit having the above described structure can be manufactured to have a slim profile.
  • the fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light.
  • a backlight unit according to an embodiment of the present invention secures high emission brightness and excellent color uniformity over positions.
  • FIG. 2 is a schematic view illustrating a liquid crystal display device according to an embodiment of the present invention.
  • a liquid crystal display device includes the above described backlight unit, a first polarizer 21, a liquid crystal panel 23, and a second polarizer 25.
  • the backlight unit includes a light emitting element 11, a light guide plate 13, a fluorescent exciting sheet 15, and a transflective polarizing prism sheet 17.
  • the light emitting element 11 may provide the light guide plate 13 with blue light.
  • the light emitting element 11 may be realized as, for example, a blue light emitting diode. Blue light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15.
  • a pattern may be formed on a lower surface of the light guide plate 13.
  • projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15.
  • a reflector may be further formed on a lower portion of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
  • the fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light.
  • the fluorescent exciting sheet 15 may be realized to include a yellow phosphor or a red/green phosphor.
  • the light emitting element 11 may provide blue/green light.
  • the light emitting element 11 may be realized as a blue light emitting diode and a green light emitting diode. Also, the light emitting element 11 may be realized to be mounted as a light emitting diode package including a blue light emitting chip and a green light emitting chip.
  • Blue/green light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15.
  • a pattern may be formed on a lower surface of the light guide plate 13.
  • projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15.
  • a reflector may be further formed on a lower surface of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
  • the fluorescent exciting sheet 15 receives blue/green light emitted from the light emitting element 11 to emit white light.
  • the fluorescent exciting sheet 15 may be realized to include a red phosphor.
  • the transflective polarizing prism sheet 17 condenses light emitted from the fluorescent exciting sheet 15, onto the liquid crystal panel 23.
  • the liquid crystal panel 23 uses light incident thereon through the transflective polarizing prism sheet 17 to display image.
  • the transflective polarizing prism sheet 17 transmits light polarized in a set direction, whereas reflects light polarized in the other directions.
  • the transflective polarizing prism sheet 17 may be realized to have a transmission axis parallel with that of the polarizer 21 attached on the bottom of the liquid crystal panel 23.
  • a backlight unit has 30 % higher brightness when using the transflective polarizing prism sheet 17 than when using a general prism sheet.
  • Upper surface of the transflective polarizing prism sheet 17 has a prism shape, and condenses light incident thereon from the fluorescent exciting sheet 15, onto the liquid crystal panel 23.
  • the second polarizing panel 25 may have a transmission axis either parallel with or nonparallel with that of the first polarizing panel 21 according to driving characteristics of the liquid crystal panel 23. According to the driving of the liquid crystal panel 23, the second polarizer 25 allows or prohibits a transmission of light incident thereon through the first polarizer 21.
  • the backlight unit or the liquid crystal display device described above may be applied to a mobile communication terminal to realize a slim mobile communication terminal.
  • a mobile communication terminal includes a communication unit for performing communication with the outside.
  • a mobile communication terminal includes the communication unit and a control unit for controlling the backlight unit or the liquid crystal display device.
  • an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile.

Abstract

Provided is a backlight unit and an LCD device having the same. The backlight unit includes a light guide plate, a light emitting element, a fluorescent exciting sheet, and a transflective polarizing prism sheet. The light emitting element provides the colored light to the light guide plate. The fluorescent exciting sheet is formed on the light guide plate, and the transflective polarizing prism sheet is formed on the fluorescent exciting sheet. The fluorescent exciting sheet receives the colored light incident thereon through the light guide plate to emit white light.

Description

Description BACKLIGHT UNIT AND LCD HAVING THE SAME
Technical Field
[1] The present invention relates to a backlight unit and a liquid crystal display (LCD) device having the same. Background Art
[2] A cathode ray tube (CRT) display device has been most widely used until recently as one of display devices for displaying image data on a screen. However, the CRT display device causes a lot of inconvenience due to its large volume and heavy weight for its display area.
[3] A thin film type flat panel display device, which has a slim profile and a large display area and thus can be used conveniently anywhere, has been developed and is gradually replacing the CRT.
[4] A liquid crystal display (LCD) device is one of the thin film type flat panel display devices, which are widely used at the present time. The LCD device uses optical anisotropy and polarization properties of liquid crystal molecules. Alignment of liquid crystal molecules has a specific direction and polarization properties because a liquid crystal has a thin and long structure. The alignment direction can be controlled by applying an electric field to the liquid crystal. Accordingly, when the alignment direction is controlled, due to the optical anisotropy of the liquid crystal, light rays may pass through or be cut off by the liquid crystal according to the alignment direction of the liquid crystal molecules so that colors and images are displayed.
[5] Meanwhile, the liquid crystal display device generally uses light provided by an external light source or a backlight unit to display images because the liquid crystal is not self-luminous.
[6] Vigorous efforts are being made to develop the backlight unit, particularly having high emission brightness and excellent color uniformity over positions along with a slim profile. Disclosure of Invention
Technical Problem
[7] An embodiment of the present invention provides a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile.
[8] An embodiment of the present invention provides an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile. Technical Solution
[9] An embodiment of the present invention provides a backlight unit comprising: a light guide plate; a light emitting element for providing the colored light to the light guide plate; a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light; and a transflective polarizing prism sheet formed on the fluorescent exciting sheet.
[10] An embodiment of the present invention provides a liquid crystal display device comprising: a backlight unit having a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; and a second polarizer formed on the liquid crystal panel.
[11] An embodiment of the present invention provides a mobile communication terminal comprising: a backlight unit having a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; a second polarizer formed on the liquid crystal panel; a communication unit for performing communication with an outside; and a control unit for controlling the backlight unit, the liquid crystal panel, and the communication unit.
Advantageous Effects
[12] According to the present invention, it is possible to provide a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile. [13] According to the present invention, it is also possible to provide an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile.
Brief Description of the Drawings [14] FIG. 1 is a schematic view illustrating a backlight unit according to an embodiment of the present invention; and [15] FIG. 2 is a schematic view illustrating a liquid crystal display device according to an embodiment of the present invention.
Best Mode for Carrying Out the Invention
[16] It will be understood that when a layer, a region, a pattern or a structure is referred to as being "on" or "under" a substrate, a layer, a region, a pad or a pattern in the descriptions of the embodiments, the term "on" may denote "directly on", or "indirectly on", and the term "under" may denote "directly under" or "indirectly under".
[17] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to accompanying drawings.
[18] FIG. 1 is a schematic view illustrating a backlight unit according to an embodiment of the present invention.
[19] A backlight unit according to an embodiment of the present invention includes a light emitting element 11, a light guide plate 13, a fluorescent exciting sheet 15, and a transflective polarizing prism sheet 17.
[20] For example, the light emitting element 11 may provide the light guide plate with blue light. The light emitting element 11 may be realized as, for example, a blue light emitting diode. Blue light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15. A pattern may be formed on a lower surface of the light guide plate 13. For example, projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15. Also, a reflector may be further formed on a lower portion of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
[21] The fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light. The fluorescent exciting sheet 15 may be realized to include a yellow phosphor or a red/green phosphor. Here, the phosphor may be contained inside the fluorescent exciting sheet 15 or coated on outer surfaces of the fluorescent exciting sheet 15.
[22] For another example, the light emitting element 11 may provide blue/green light.
The light emitting element 11 may be realized as a blue light emitting diode and a green light emitting diode. Also, the light emitting element 11 may be realized to be mounted as a light emitting diode package including a blue light emitting chip and a green light emitting chip. The blue/green light may be expressed as cyan light.
[23] Blue/green light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15. A pattern may be formed on a lower surface of the light guide plate 13. For example, projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15. In addition, a reflector may be further formed on a lower surface of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
[24] The fluorescent exciting sheet 15 receives blue/green light emitted from the light emitting element 11 to emit white light. The fluorescent exciting sheet 15 may be realized to include a red phosphor. Here, the phosphor may be contained inside the fluorescent exciting sheet 15 or coated on outer surfaces of the fluorescent exciting sheet 15.
[25] Meanwhile, white light emitted from the fluorescent exciting sheet 15 is incident on the transflective polarizing prism sheet 17. The transflective polarizing prism sheet 17 transmits light (Pl) polarized in a first direction, whereas reflects light (P2) polarized in a second direction perpendicular to the first direction. Also, light that has been reflected from the transflective polarizing prism sheet 17 is reflected back from the fluorescent exciting sheet 15 disposed under the transflective polarizing prism sheet 17, so that a portion of the reflected light (Pl) can now pass through the transflective polarizing prism sheet 17. Accordingly, a backlight unit has 30 % higher brightness when using the transflective polarizing prism sheet 17 than when using a general prism sheet. Upper surface of the transflective polarizing prism sheet 17 has a prism shape.
[26] White light emitted from the fluorescent exciting sheet 15 is unpolarized light including both a polarization component in a first direction (Pl) and a polarization component in a second direction (P2). The transflective polarizing prism sheet 17 transmits light having the polarization component in the first direction (Pl), whereas reflects light having the polarization component in the second direction (P2) according to a characteristic of the polarization axis thereof. Also, as described above, light that has been reflected from the transflective polarizing prism sheet 17 is reflected back from the fluorescent exciting sheet 15 disposed under the transflective polarizing prism sheet 17, so that a portion of the reflected light (Pl) having the polarization component in the first direction (Pl) can now pass through the transflective polarizing prism sheet 17. Light excited to white light through the fluorescent exciting sheet 15 does not affect a color coordinate of the backlight though it recycles repeatedly.
[27] A backlight unit having the above described structure can be manufactured to have a slim profile. In addition, the fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light. Thus, a backlight unit according to an embodiment of the present invention secures high emission brightness and excellent color uniformity over positions.
[28] FIG. 2 is a schematic view illustrating a liquid crystal display device according to an embodiment of the present invention. [29] A liquid crystal display device according to an embodiment of the present invention includes the above described backlight unit, a first polarizer 21, a liquid crystal panel 23, and a second polarizer 25. The backlight unit includes a light emitting element 11, a light guide plate 13, a fluorescent exciting sheet 15, and a transflective polarizing prism sheet 17.
[30] For example, the light emitting element 11 may provide the light guide plate 13 with blue light. The light emitting element 11 may be realized as, for example, a blue light emitting diode. Blue light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15. A pattern may be formed on a lower surface of the light guide plate 13. For example, projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15. Also, a reflector may be further formed on a lower portion of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
[31] The fluorescent exciting sheet 15 receives blue light emitted from the light emitting element 11 to emit white light. The fluorescent exciting sheet 15 may be realized to include a yellow phosphor or a red/green phosphor.
[32] For another example, the light emitting element 11 may provide blue/green light.
The light emitting element 11 may be realized as a blue light emitting diode and a green light emitting diode. Also, the light emitting element 11 may be realized to be mounted as a light emitting diode package including a blue light emitting chip and a green light emitting chip.
[33] Blue/green light emitted from the light emitting element 11 passes through the light guide plate 13, and then is incident on the fluorescent exciting sheet 15. A pattern may be formed on a lower surface of the light guide plate 13. For example, projections may be formed on the lower surface of the light guide plate 13. The projections contribute to making the light emitted from the light emitting element 11 be received by the fluorescent exciting sheet 15. In addition, a reflector may be further formed on a lower surface of the light guide plate 13. The reflector reflects light that has leaked to a lower portion of the light guide plate 13 back in an upper direction.
[34] The fluorescent exciting sheet 15 receives blue/green light emitted from the light emitting element 11 to emit white light. The fluorescent exciting sheet 15 may be realized to include a red phosphor.
[35] The transflective polarizing prism sheet 17 condenses light emitted from the fluorescent exciting sheet 15, onto the liquid crystal panel 23. The liquid crystal panel 23 uses light incident thereon through the transflective polarizing prism sheet 17 to display image. [36] The transflective polarizing prism sheet 17 transmits light polarized in a set direction, whereas reflects light polarized in the other directions. For example, the transflective polarizing prism sheet 17 may be realized to have a transmission axis parallel with that of the polarizer 21 attached on the bottom of the liquid crystal panel 23. In this case, light polarized to pass through the first polarizer 21 attached on the bottom of the liquid crystal panel 23 passes through the transflective polarizing prism sheet 17, and then is incident on the liquid crystal panel 23. Also, light reflected from the transflective polarizing prism sheet 17 is reflected back from elements disposed below the transflective polarizing prism sheet 17. A portion of the light reflected back passes through the transflective polarizing prism sheet 17, and then is incident on the liquid crystal panel 23. Accordingly, a backlight unit has 30 % higher brightness when using the transflective polarizing prism sheet 17 than when using a general prism sheet. Upper surface of the transflective polarizing prism sheet 17 has a prism shape, and condenses light incident thereon from the fluorescent exciting sheet 15, onto the liquid crystal panel 23.
[37] The second polarizing panel 25 may have a transmission axis either parallel with or nonparallel with that of the first polarizing panel 21 according to driving characteristics of the liquid crystal panel 23. According to the driving of the liquid crystal panel 23, the second polarizer 25 allows or prohibits a transmission of light incident thereon through the first polarizer 21.
[38] The backlight unit or the liquid crystal display device described above may be applied to a mobile communication terminal to realize a slim mobile communication terminal.
[39] A mobile communication terminal according to an embodiment of the present invention includes a communication unit for performing communication with the outside. A mobile communication terminal according to an embodiment of the present invention includes the communication unit and a control unit for controlling the backlight unit or the liquid crystal display device. Mode for the Invention
[40] While the present invention has been described and illustrated herein with reference to the preferred embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention that come within the scope of the appended claims and their equivalents. Industrial Applicability
[41] According to the present invention, it is possible to provide a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile.
[42] According to the present invention, it is also possible to provide an LCD device and a mobile communication terminal including a backlight unit having high emission brightness and excellent color uniformity over positions along with a slim profile, so that it can be manufactured to have a slimmer profile.

Claims

Claims
[ 1 ] A backlight unit comprising: a light guide plate; a light emitting element for providing the colored light to the light guide plate; a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light; and a transflective polarizing prism sheet formed on the fluorescent exciting sheet.
[2] The backlight unit according to claim 1, wherein the light emitting element comprises a blue light emitting diode, and the fluorescent exciting sheet comprises one of a yellow phosphor and a red/green phosphor.
[3] The backlight unit according to claim 1, wherein the light emitting element comprises a blue light emitting diode and a green light emitting diode, and the fluorescent exciting sheet comprises a red phosphor.
[4] The backlight unit according to claim 1, wherein the transflective polarizing prism sheet transmits light polarized in a first direction, whereas reflects light polarized in a second direction perpendicular to the first direction, and an upper surface thereof has a prism shape.
[5] The backlight unit according to claim 1, comprising a reflector formed in a lower portion of the light guide plate.
[6] The backlight unit according to claim 1, wherein a pattern is formed on a lower surface of the light guide plate.
[7] The backlight unit according to claim 1, wherein white light emitted from the fluorescent exciting sheet is unpolarized light.
[8] A liquid crystal display device comprising: a backlight unit including a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; and a second polarizer formed on the liquid crystal panel.
[9] The liquid crystal display device according to claim 8, wherein the transflective polarizing prism sheet has a transmission axis parallel with a transmission axis of the first polarizer.
[10] The liquid crystal display device according to claim 8, wherein the light emitting element comprises a blue light emitting diode, and the fluorescent exciting sheet comprises one of a yellow phosphor and a red/green phosphor.
[11] The liquid crystal display device according to claim 8, wherein the light emitting element comprises a blue light emitting diode and a green light emitting diode, and the fluorescent exciting sheet comprises a red phosphor.
[12] The liquid crystal display device according to claim 8, wherein the transflective polarizing prism sheet transmits light polarized in a first direction, whereas reflects light polarized in a second direction perpendicular to the first direction, and an upper surface thereof has a prism shape.
[13] The liquid crystal display device according to claim 8, comprising a reflector formed under the light guide plate.
[14] The liquid crystal display device according to claim 8, wherein white light emitted from the fluorescent exciting sheet is unpolarized light.
[15] A mobile communication terminal comprising: a backlight unit including a light guide plate, a light emitting element for providing the colored light to the light guide plate, a fluorescent exciting sheet formed on the light guide plate to receive the colored light incident thereon through the light guide plate and emit white light, and a transflective polarizing prism sheet formed on the fluorescent exciting sheet; a liquid crystal panel receiving light provided by the backlight unit; a first polarizer formed under the liquid crystal panel; a second polarizer formed on the liquid crystal panel; a communication unit for performing communication with an outside; and a control unit for controlling the backlight unit, the liquid crystal panel, and the communication unit.
[16] The mobile communication terminal according to claim 15, wherein the transflective polarizing prism sheet has a transmission axis parallel with a transmission axis of the first polarizer.
[17] The mobile communication terminal according to claim 15, wherein the light emitting element comprises a blue light emitting diode, and the fluorescent exciting sheet comprises one of a yellow phosphor and a red/green phosphor.
[18] The mobile communication terminal according to claim 15, wherein the light emitting element comprises a blue light emitting diode and a green light emitting diode, and the fluorescent exciting sheet comprises a red phosphor.
[19] The mobile communication terminal according to claim 15, wherein the transflective polarizing prism sheet transmits light polarized in a first direction, whereas reflects light polarized in a second direction perpendicular to the first direction, and an upper surface thereof has a prism shape.
[20] The mobile communication terminal according to claim 15, wherein white light emitted from the fluorescent exciting sheet is unpolarized light.
PCT/KR2007/000033 2006-01-24 2007-01-03 Backlight unit and lcd having the same WO2007086657A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
KR10-2006-0007185 2006-01-24
KR1020060007186A KR20070077574A (en) 2006-01-24 2006-01-24 Backlight unit and lcd having the same
KR1020060007185A KR20070077573A (en) 2006-01-24 2006-01-24 Backlight unit and lcd having the same
KR10-2006-0007186 2006-01-24

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US9857519B2 (en) 2012-07-03 2018-01-02 Oree Advanced Illumination Solutions Ltd. Planar remote phosphor illumination apparatus
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